The law of conservation of matter teaches that one new molecule of carbon dioxide entering the atmosphere from oxidation of one atom of carbon is matched by the loss of one molecule of oxygen. On a planetary scale, the 50-year rise in atmospheric carbon dioxide from 300 to 400 parts per million (a 33 percent increase) means that atmospheric oxygen has decreased by at least 100 parts per million over the same period.
Despite the fact that a change of this magnitude is barely measurable from, say, 20.80 percent to 20.79 percent, it is not difficult to visualize the consequence of an unchecked increase in atmospheric carbon dioxide, regardless of its direct impact on global warming.
Until the political will is found to cap worldwide carbon dioxide emissions, the decline in atmospheric oxygen will continue, moving from imperceptible to detectable. Will one impact on human life be no more athletic records? When will the deniers of carbon-dioxide-driven climate change wake up?